The present invention relates to a solid-state laser device, and in particular, to a solid-state laser device, in which an output of a semiconductor-pumped solid-state laser device is controlled.
Referring to FIG. 5, description will be given below on general features of a semiconductor-pumped solid laser device.
In FIG. 5, reference numeral 1 denotes a light emitter which has a single diode or a plurality of laser diodes for emitting a laser beam with a wavelength λ as an excitation light. Reference numeral 2 represents a resonator for outputting a laser beam with a wavelength λ1.
The resonator 2 primarily comprises a reflection mirror 3, an output mirror 4 arranged at a position opposite to the reflection mirror 3, and a laser crystal 5 disposed on an optical axis of the output mirror 4 and the reflection mirror 3. On the reflection mirror 3 and the output mirror 4, a dielectric reflection films 6 and 7 are formed respectively.
On an optical axis on an output side of the resonator 2, a partial mirror 8 is disposed, and the partial mirror 8 splits the laser beam outputted from the resonator 2 and projects a part of the laser beam toward a photodetector 9 for monitoring. A photodetection signal from the photodetector 9 for monitoring is inputted to a control unit 11, and the control unit 11 controls the light emitter 1 so that the intensity of an output light from the resonator 2 is maintained at a constant level.
As the laser crystal 5, YAG (yttrium aluminum garnet) or YVO4 doped with Nd3+ ions is used, for instance.
In the semiconductor-pumped solid-state laser device as described above, when the light emitter 1 is driven, an excitation light is emitted to the resonator 2 through the reflection mirror 3. The excitation light passes through the laser crystal 5 and is pumped between the dielectric reflection films 6 and 7 and is amplified. Then, a laser beam 12 with a wavelength λ1 is outputted through the output mirror 4.
The laser beam 12 is projected through the partial mirror 8 and is split by the partial mirror 8 and enters the photodetector 9 for monitoring. The photodetection signal from the photodetector 9 for monitoring is inputted to the control unit 11. Based on the photodetection signal, the control unit 11 controls the driving of the light emitter 1 so that the intensity of the laser beam 12 is maintained at a constant level.
When a control signal for setting the intensity of the laser beam 12 from the resonator 2 is inputted to the control unit 11 (see FIG. 6(A)), a driving current to be supplied to the light emitter 1 is controlled so that the intensity of the laser beam 12 is maintained at a constant level (see FIG. 6(C)). Because the driving current must respond to fluctuation of values such as a temperature of the laser crystal 5, the driving current is not at constant level (see FIG. 6(B)).
In a prior application (Japanese Patent Application 2002-335683), the present applicants have proposed a solid-state laser device which comprises a plurality of resonators sharing an optical axis.
The solid-state laser device as proposed above is advantageous in that the output of the laser beam is increased, and a plurality of laser beams with different wavelengths can be outputted, and the structure of the device can be formed in simple design.